1. Field of the Invention
The present invention relates to an image display apparatus, a driving method of the image display apparatus, an image display apparatus assembly employing the image display apparatus and a driving method of the image display apparatus assembly.
2. Description of the Related Art
In recent years, in the case of an image display apparatus such as a color liquid-crystal display apparatus for example, the increased performance raises a problem of the increased power consumption. In particular, with the improved fineness, the widened color reproduction range and the increased luminance, in the case of the color liquid-crystal display apparatus for example, the power consumption of the backlight undesirably rises. In order to solve these problems, attention is paid to a technology for improving the luminance of the display by making use of a white-color display sub-pixel for displaying a white color. In accordance with the technology, a display pixel is configured to include four sub-pixels which are typically the white-color display sub-pixel in addition to three other sub-pixels. i.e., a red-color display sub-pixel for displaying a red color, a green-color display sub-pixel for displaying a green color and a blue-color display sub-pixel for displaying a blue color. In addition, with the same power consumption as the existing image display apparatus, the configuration based on the four sub-pixels gives a high luminance and, therefore, the power consumption of the backlight can be reduced to provide the same luminance as the existing image display apparatus.
In this case, as an example, a color-image display apparatus disclosed in Japanese Patent No. 3167026 employs:
means for generating color signals of three different types in an additive color three elementary color process from an input signal; and
means for generating an auxiliary signal by carrying out an additive color process on the color signals having different hues at equal rates and for providing a display section with four different type display signals, i.e., the auxiliary signal and three different-type color signals which are each obtained by subtracting the auxiliary signal from one of the three different color signals having three different hues.
It is to be noted that the color signals of three different types are used for driving the red-color display sub pixel, the green-color display sub pixel and the blue-color display sub pixel respectively. On the other hand, the auxiliary signal is used for driving the white-color display sub pixel.
In addition, Japanese Patent No. 3805150 discloses a liquid-crystal display apparatus capable of color displaying. The liquid-crystal display apparatus is provided with a liquid-crystal panel employing main pixel units which each has a red-color output sub-pixel, a green-color output sub-pixel, a blue-color output sub-pixel, and an intensity sub-pixel. The liquid-crystal display apparatus has operating means for making use of digital values Ri, Gi and Bi, which are obtained for the red-color input sub-pixel, the green-color input sub-pixel and the blue-color input sub-pixel respectively from an input image signal, for finding a digital value W for an intensity sub-pixel as well as a digital value Ro for driving the red-color output sub-pixel, a digital value Go for driving the green-color output sub-pixel and a digital value Bo for the blue-color output sub-pixel. The operating means is characterized in that the operating means finds a digital value Ro, a digital value Go, a digital value Bo and a digital value W which satisfy the following conditions:
Ri:Gi:Bi=(Ro+W):(Go+W):(Bo+W), and
the values Ro, Go, Bo and W improve the luminance by virtue of the addition of the luminance sub-pixel in a comparison with the configuration including only the red-color input sub-pixel, the green-color input sub-pixel and the blue-color input sub-pixel.